Issue link: https://iconnect007.uberflip.com/i/357479
60 SMT Magazine • August 2014 • BGA warping: incorrect reflow profile set- tings may cause the BGA substrate to change shape, bringing the attached solder balls out of contact with solder paste • Contamination: any foreign matter or ox- idation of solder paste may cause solder joint defects which are likely to cause early failure and require field repairs. These defects include head-in-pillow and voiding stencil Print/Placement Issues • Misalignment, bridging, incorrect solder paste volume Automated solder ball inspection typically requires three slices through the solder joint to determine if the connection is complete or a reflow defect occurred near the PCB or BGA device. Pth Barrel Fill Through-hole components have leads sol- dered to metal-plated holes (vias) through the PCB. The IPC-A-610 standard defines that the amount of solder in the via barrel must cover at least 75% of the board thickness to be accept- able for Class 3 high performance products. INtRODuCtION tO INLINE aXI tEChNOLOgy continues aRTIClE Figure 16: BGA inspection using 3D slice images reveals reflow problems. No reflow (1); normal (2); non-wetting at PCB (3); non-wetting at BGA (4).